Gas turbine engines typically have fuel supply systems for delivering fuel to a combustor, where the fuel is ignited to produce a thrust. In many engines, the fuel is stored in a fuel source, such as a fuel tank, and is drawn out by one or more pumps. The pumps pressurize the fuel and deliver the pressurized fuel to manifolds in the combustor via a main supply line. To control the rate at which the fuel flows through the system, the main supply line may include one or more valves in flow series between the pumps and the fuel manifolds. These valves generally include at least a main metering valve and a bypass valve downstream thereof. The bypass valve may be disposed in a bypass flow line connected upstream of the metering valve for allowing a portion of the fuel flowing in the main supply line back to the inlet of the one or more pumps.
During operation, it may be desirable to determine a flow rate across the main metering valve to establish whether the bypass valve should be used or whether to change the flow rate of the fuel through the system. In this regard, a position sensor may be coupled to the main metering valve. The position sensor can include various components such as a rotor, a stator, and primary and secondary windings. The rotor is typically coupled to the main metering valve, and the primary winding, which is disposed on the rotor, is used as a reference winding to which the secondary winding on the stator is compared. Thus, when the flow rate across the main metering valve changes, the rotor changes rotational position to thereby produce a positional difference between the reference winding and the secondary winding. The positional difference is then communicated to a controller, which determines whether to send a signal to increase or decrease the flow rate across the main metering valve.
Although the aforementioned systems are adequate for use in conventional engines, they may be improved. For example, in some engines, the position sensor components are disposed in a housing having a chamber that is in fluid communication with the system. In some cases, the housing chamber may be filled with or exposed to fuel from the system. As engine power output demands increase, engine operating temperatures tend to increase as well, causing the position sensor components to be subjected to high-temperature fuels (e.g., fuels having a temperature greater than about 180° C.). The high-temperature fuels may decrease the useful life of the position sensor components, in particular, the primary and secondary copper windings. As a result, the position sensors may be replaced more frequently than when exposed to lower temperature fuels, and the maintenance costs of the engine may undesirably increase.
Accordingly, it is desirable to have a fuel delivery system that can be employed in high temperature environments. In addition, it is desirable for the system to include assemblies that include components, such as position sensors, may be exposed to high-temperature fuels (e.g., greater than 180° C.). Furthermore, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter.